<template>
 <div class="music-list">
     <div class="back" @click="back">
         <i class="icon-back"></i>
     </div>
     <h1 class="title" v-html="title"></h1>
     <div class="bg-image" :style="bgStyle" ref="bgImage">
         <div class="play-wrapper" >
           <div class="play" v-show="songs.length>0" ref="playBtn" @click="random">
              <i class="icon-play"></i>
              <span class="text">随机播放全部</span>
           </div>
         </div>
         <div class="filter" ref="filter"></div>
     </div>
     <div class="bg-layer" ref="layer"></div>
     <scroll @scroll="scroll" :probe-type="probeType" :listen-scroll="listenScroll" 
     :data="songs" class="list" ref="list">
       <div class="song-list-wrapper">
         <song-list @select="selectItem" :songs="songs"></song-list>
       </div>
       <div class="loading-container" v-show="!songs.length">
         <loading></loading>
       </div>
     </scroll>
 </div> 
</template>

<script type="text/ecmascript-6">
    import Scroll from 'base/scroll/scroll'
    import SongList from 'base/song-list/song-list'
    import Loading from 'base/loading/loading'
    import {prefixStyle} from 'common/js/dom'
    import {mapActions} from 'vuex'
    import {playlistMixin} from 'common/js/mixin'

    const RESERVED_HEIGHT=40
    const transform=prefixStyle('transform')
    const backdrop=prefixStyle('backdrop-filter')

    export default{
      mixins:[playlistMixin],
       props:{
         bgImage:{
            type:String,
            default:''
        },
        songs:{
            type:Array,
            default:[]
        },
        title:{
            type:String,
            default:''
        }
      },
      data(){
        return{
          scrollY:0
        }
      },
      computed:{
          bgStyle(){
              return `background-image:url(${this.bgImage})`
          }
      },
      created(){
        this.probeType=3
        this.listenScroll=true
      },
      mounted(){
        this.imageHeight=this.$refs.bgImage.clientHeight
        this.minTranslateY=-this.imageHeight+RESERVED_HEIGHT
        this.$refs.list.$el.style.top=`${this.imageHeight}px`
      },
      methods:{
        handlePlaylist(playlist){
          const bottom=playlist.length>0?'60px':''
          this.$refs.list.$el.style.bottom=bottom
          this.$refs.list.refresh()
        },
        scroll(pos){
          this.scrollY=pos.y
        },
        back(){
          this.$router.back()
        },
        selectItem(item,index){
          this.selectPlay({
            list:this.songs,
            index
          })
        },
        random(){
          this.randomPlay({
            list:this.songs
          })
        },
        ...mapActions([
          'selectPlay',
          'randomPlay'
        ])
      },
      watch:{
        scrollY(newY){
          let translateY=Math.max(this.minTranslateY,newY)
          let zIndex=0
          let scale=1
          let blur=0
          this.$refs.layer.style[transform]=`translate3d(0,${translateY}px,0)`
          const percent=Math.abs(newY/this.imageHeight)
          if(newY>0){
            scale=1+percent
            zIndex=10
          }else{
            blur=Math.min(20*percent)
          }
          this.$refs.filter.style[backdrop]=`blur(${blur}px)`

          if(newY<this.minTranslateY){
              zIndex=10
              this.$refs.bgImage.style.paddingTop=0
              this.$refs.bgImage.style.height=`${RESERVED_HEIGHT}px`
              this.$refs.playBtn.style.display='none'
          }else{
              this.$refs.bgImage.style.paddingTop=`70%`
              this.$refs.bgImage.style.height=0
              this.$refs.playBtn.style.display=''
          }
          this.$refs.bgImage.style.zIndex=zIndex
          this.$refs.bgImage.style[transform]=`scale(${scale})`

        }
      },
      components:{
        Scroll,
        SongList,
        Loading
      }
    }
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
    @import "~common/stylus/variable"
    @import "~common/stylus/mixin"

  .music-list
    position: fixed
    z-index: 100
    top: 0
    left: 0
    bottom: 0
    right: 0
    background: $color-background
    .back
      position absolute
      top: 0
      left: 6px
      z-index: 50
      .icon-back
        display: block
        padding: 10px
        font-size: $font-size-large-x
        color: $color-theme
    .title
      position: absolute
      top: 0
      left: 10%
      z-index: 40
      width: 80%
      no-wrap()
      text-align: center
      line-height: 40px
      font-size: $font-size-large
      color: $color-text
    .bg-image
      position: relative
      width: 100%
      height: 0
      padding-top: 70%
      transform-origin: top
      background-size: cover
      .play-wrapper
        position: absolute
        bottom: 20px
        z-index: 50
        width: 100%
        .play
          box-sizing: border-box
          width: 135px
          padding: 7px 0
          margin: 0 auto
          text-align: center
          border: 1px solid $color-theme
          color: $color-theme
          border-radius: 100px
          font-size: 0
          .icon-play
            display: inline-block
            vertical-align: middle
            margin-right: 6px
            font-size: $font-size-medium-x
          .text
            display: inline-block
            vertical-align: middle
            font-size: $font-size-small
      .filter
        position: absolute
        top: 0
        left: 0
        width: 100%
        height: 100%
        background: rgba(7, 17, 27, 0.4)
    .bg-layer
      position: relative
      height: 100%
      background: $color-background
    .list
      position: fixed
      top: 0
      bottom: 0
      width: 100%
      background: $color-background
      .song-list-wrapper
        padding: 20px 30px
      .loading-container
        position: absolute
        width: 100%
        top: 50%
        transform: translateY(-50%)
</style>